Add text cursor support.

This turned out to be much more complex than anticipated, and the
potential for bugs is therefore quite high.

1 files changed, 179 insertions, 6 deletions

diff --git a/src/entry_backend/pango.c b/src/entry_backend/pango.c
index 82c93ee..d274950 100644
--- a/src/entry_backend/pango.c
+++ b/src/entry_backend/pango.c
@@ -77,6 +77,127 @@ static void render_text_themed(
 	pango_cairo_show_layout(cr, layout);
 }
 
+static void render_input(
+		cairo_t *cr,
+		PangoLayout *layout,
+		const char *text,
+		uint32_t text_length,
+		const struct text_theme *theme,
+		uint32_t cursor_position,
+		const struct cursor_theme *cursor_theme,
+		PangoRectangle *ink_rect,
+		PangoRectangle *logical_rect)
+{
+	struct directional padding = theme->padding;
+	struct color color = theme->foreground_color;
+	cairo_set_source_rgba(cr, color.r, color.g, color.b, color.a);
+
+	pango_layout_set_text(layout, text, -1);
+	pango_cairo_update_layout(cr, layout);
+	pango_cairo_show_layout(cr, layout);
+
+	pango_layout_get_pixel_extents(layout, ink_rect, logical_rect);
+
+	double extra_cursor_advance = 0;
+	if (cursor_position == text_length && cursor_theme->show) {
+		switch (cursor_theme->style) {
+			case CURSOR_STYLE_BAR:
+				extra_cursor_advance = cursor_theme->thickness;
+				break;
+			case CURSOR_STYLE_BLOCK:
+				extra_cursor_advance = cursor_theme->em_width;
+				break;
+			case CURSOR_STYLE_UNDERSCORE:
+				extra_cursor_advance = cursor_theme->em_width;
+				break;
+		}
+		extra_cursor_advance += logical_rect->width
+			- logical_rect->x
+			- ink_rect->width;
+	}
+
+	if (theme->background_color.a != 0) {
+		cairo_save(cr);
+		color = theme->background_color;
+		cairo_set_source_rgba(cr, color.r, color.g, color.b, color.a);
+		cairo_translate(
+				cr,
+				floor(-padding.left + ink_rect->x),
+				-padding.top);
+		rounded_rectangle(
+				cr,
+				ceil(ink_rect->width + extra_cursor_advance + padding.left + padding.right),
+				ceil(logical_rect->height + padding.top + padding.bottom),
+				theme->background_corner_radius
+				);
+		cairo_fill(cr);
+		cairo_restore(cr);
+
+		color = theme->foreground_color;
+		cairo_set_source_rgba(cr, color.r, color.g, color.b, color.a);
+
+		pango_cairo_show_layout(cr, layout);
+	}
+
+	if (!cursor_theme->show) {
+		/* No cursor to draw, we're done. */
+		return;
+	}
+
+	double cursor_x;
+	double cursor_width;
+
+	if (cursor_position == text_length) {
+		cursor_x = logical_rect->width + logical_rect->x;
+		cursor_width = cursor_theme->em_width;
+	} else {
+		/*
+		 * Pango wants a byte index rather than a character index for
+		 * the cursor position, so we have to calculate that here.
+		 */
+		const char *tmp = text;
+		for (size_t i = 0; i < cursor_position; i++) {
+			tmp = utf8_next_char(tmp);
+		}
+		uint32_t start_byte_index = tmp - text;
+		uint32_t end_byte_index = utf8_next_char(tmp) - text;
+		PangoRectangle start_pos;
+		PangoRectangle end_pos;
+		pango_layout_get_cursor_pos(layout, start_byte_index, &start_pos, NULL);
+		pango_layout_get_cursor_pos(layout, end_byte_index, &end_pos, NULL);
+		cursor_x = (double)start_pos.x / PANGO_SCALE;
+		cursor_width = (double)(end_pos.x - start_pos.x) / PANGO_SCALE;;
+	}
+
+	cairo_save(cr);
+	color = cursor_theme->color;
+	cairo_set_source_rgba(cr, color.r, color.g, color.b, color.a);
+	cairo_translate(cr, cursor_x, 0);
+	switch (cursor_theme->style) {
+		case CURSOR_STYLE_BAR:
+			rounded_rectangle(cr, cursor_theme->thickness, logical_rect->height, cursor_theme->corner_radius);
+			cairo_fill(cr);
+			break;
+		case CURSOR_STYLE_BLOCK:
+			rounded_rectangle(cr, cursor_width, logical_rect->height, cursor_theme->corner_radius);
+			cairo_fill_preserve(cr);
+			cairo_clip(cr);
+			cairo_translate(cr, -cursor_x, 0);
+			color = cursor_theme->text_color;
+			cairo_set_source_rgba(cr, color.r, color.g, color.b, color.a);
+			pango_cairo_show_layout(cr, layout);
+			break;
+		case CURSOR_STYLE_UNDERSCORE:
+			cairo_translate(cr, 0, cursor_theme->underline_depth);
+			rounded_rectangle(cr, cursor_width, cursor_theme->thickness, cursor_theme->corner_radius);
+			cairo_fill(cr);
+			break;
+	}
+
+	logical_rect->width += extra_cursor_advance;
+	cairo_restore(cr);
+}
+
 void entry_backend_pango_init(struct entry *entry, uint32_t *width, uint32_t *height)
 {
 	cairo_t *cr = entry->cairo[0].cr;
@@ -97,7 +218,6 @@ void entry_backend_pango_init(struct entry *entry, uint32_t *width, uint32_t *he
 				entry->font_variations);
 	}
 	pango_context_set_font_description(context, font_description);
-	pango_font_description_free(font_description);
 
 	entry->pango.layout = pango_layout_new(context);
 
@@ -109,6 +229,33 @@ void entry_backend_pango_init(struct entry *entry, uint32_t *width, uint32_t *he
 		pango_layout_set_attributes(entry->pango.layout, attr_list);
 	}
 
+	log_debug("Loading Pango font.\n");
+	PangoFontMap *map = pango_cairo_font_map_get_default();
+	PangoFont *font = pango_font_map_load_font(map, context, font_description);
+	PangoFontMetrics *metrics = pango_font_get_metrics(font, NULL);
+	hb_font_t *hb_font = pango_font_get_hb_font(font);
+
+	uint32_t m_codepoint;
+	if (hb_font_get_glyph_from_name(hb_font, "m", -1, &m_codepoint)) {
+		entry->cursor_theme.em_width = (double)hb_font_get_glyph_h_advance(hb_font, m_codepoint) / PANGO_SCALE;
+	} else {
+		entry->cursor_theme.em_width = (double)pango_font_metrics_get_approximate_char_width(metrics) / PANGO_SCALE;
+	}
+
+	entry->cursor_theme.underline_depth = (double)
+		(
+		 pango_font_metrics_get_ascent(metrics)
+		 - pango_font_metrics_get_underline_position(metrics)
+		) / PANGO_SCALE;
+	if (entry->cursor_theme.style == CURSOR_STYLE_UNDERSCORE && !entry->cursor_theme.thickness_specified) {
+		entry->cursor_theme.thickness = pango_font_metrics_get_underline_thickness(metrics) / PANGO_SCALE;
+	}
+
+	pango_font_metrics_unref(metrics);
+	g_object_unref(font);
+	log_debug("Loaded.\n");
+
+	pango_font_description_free(font_description);
 
 	entry->pango.context = context;
 }
@@ -148,7 +295,6 @@ void entry_backend_pango_update(struct entry *entry)
 	PangoLayout *layout = entry->pango.layout;
 
 	cairo_save(cr);
-	struct color color = entry->foreground_color;
 
 	/* Render the prompt */
 	PangoRectangle ink_rect;
@@ -160,7 +306,16 @@ void entry_backend_pango_update(struct entry *entry)
 
 	/* Render the entry text */
 	if (entry->input_utf8_length == 0) {
-		render_text_themed(cr, layout, entry->placeholder_text, &entry->placeholder_theme, &ink_rect, &logical_rect);
+		render_input(
+				cr,
+				layout,
+				entry->placeholder_text,
+				utf8_strlen(entry->placeholder_text),
+				&entry->placeholder_theme,
+				0,
+				&entry->cursor_theme,
+				&ink_rect,
+				&logical_rect);
 	} else if (entry->hide_input) {
 		size_t nchars = entry->input_utf32_length;
 		size_t char_size = entry->hidden_character_utf8_length;
@@ -172,14 +327,32 @@ void entry_backend_pango_update(struct entry *entry)
 		}
 		buf[char_size * nchars] = '\0';
 
-		render_text_themed(cr, layout, buf, &entry->placeholder_theme, &ink_rect, &logical_rect);
+		render_input(
+				cr,
+				layout,
+				buf,
+				entry->input_utf32_length,
+				&entry->input_theme,
+				entry->cursor_position,
+				&entry->cursor_theme,
+				&ink_rect,
+				&logical_rect);
 		free(buf);
 	} else {
-		render_text_themed(cr, layout, entry->input_utf8, &entry->input_theme, &ink_rect, &logical_rect);
+		render_input(
+				cr,
+				layout,
+				entry->input_utf8,
+				entry->input_utf32_length,
+				&entry->input_theme,
+				entry->cursor_position,
+				&entry->cursor_theme,
+				&ink_rect,
+				&logical_rect);
 	}
 	logical_rect.width = MAX(logical_rect.width, (int)entry->input_width);
 
-	color = entry->foreground_color;
+	struct color color = entry->foreground_color;
 	cairo_set_source_rgba(cr, color.r, color.g, color.b, color.a);
 
 	uint32_t num_results;